Effectiveness and Safety of Standard-Dose Non vitamin K Antagonist Oral Anticoagulants and Warfarin Among Patients With Atrial Fibrillation With a Single Stroke Risk Factor - A Nationwide Cohort Study

Main results

For the main effectiveness endpoint of ischemic stroke/systemic embolism, 103 events (80.5% as primary diagnoses) were observed within the first year, representing a rate between 0.65 and 1.20 per 100 person-years.

The estimated effect sizes in terms of HRs of the NOACs ranged between 0.81 (95%CI: 0.49-1.34) and 1.46 (0.79-2.70), with all treatment groups displaying statistically non-significant differences compared with warfarin.

There was a significantly lower risk of all-cause mortality across all treatment groups compared with warfarin, although effect sizes became non-significant when they were restricted to patients who were hospitalized with AF.

When restricting the study population to patients without conditions associated with increased mortality (HF, chronic pulmonary disease, or cancer), all effect estimates were lower for NOAC agents compared with warfarin, while only treatment with rivaroxaban reached a statistically significant lower death rate (HR: 0.39; 95%CI: 0.17-0.91).

A total of 157 any bleeding events (90% primary diagnoses) were observed during the first year. The weighted event rates ranged between 0.57 (apixaban) and 1.53 (warfarin).

Conclusion

In a Danish observational cohort study, the risk of an ischemic stroke or systemic embolism was similar between NOACs compared with warfarin in AF patients with a single non-sex stroke CHA2DS2-VASc risk factor. Lower mortality rates were seen for all NOACs compared with warfarin, but this appeared to be the consequence of selective prescription patterns. The risk of any bleeding was lower for apixaban and dabigatran compared with warfarin.

These data should be interpreted with caution because of possible residual unmeasured confounding due to selective prescribing and unobserved comorbidities, or other factors known to influence treatment selection that were not present in the data set.